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Color Theory Part 2

Continuing with color, light and their relationship with painting and drawing...

These light waves which are visible to the person of normal eyesight constitute but a small proportion of all the light rays which exist.

We are color-blind to waves longer than about 0.0007 millimeters (the approximate length of red rays) or shorter than about 0.0004 millimeters (the approximate length of violet rays), many others, including the infrared and ultraviolet, being invisible under customary conditions.

Newton followed his experiment of separating white light into the prismatic spectrum by a second, in which he passed a portion of this colored band through an aperture in another screen, permitting it to traverse a second prism.

As he found no additional change of color he was convinced that monochromatic light could be no further decomposed.

Newton also demonstrated that not only can white light be decomposed into many colors by a prism (such experiments are often carried out today with the spectroscope or similar apparatus), but that these colors can be recombined into white light.

This can be proved by impressing such colors on a second prism, or by receiving them from the original prism onto mirrors or lenses so curved as to convey all to a single spot where they will reunite to form white.

Thus, it was long ago shown beyond reasonable doubt that light is the source of color, and that white light, which seems so simple and pure, is, in reality, made up of varying rays, each capable of producing the sensation of a distinct hue.

It is obvious, then, that when light is present, color is present; when light is absent, color is absent.

It follows, too, that the nature of light influences the nature of color.

Objects look different under daylight, incandescent light, fluorescent light, colored light, etc.

The light from the sun is usually considered as white; actually, as it reaches us through the atmosphere, it is often far from pure.

With this as a background, let us consider why one object looks red and another green.

If we glance at a given object (excepting self-luminous, fluorescent or transparent ones which would bring us into a discussion more involved than we need enter here), we are able to see it by the light cast upon it and reflected to the eye.

It is easy to understand that, if the object is in strong light, it reflects much light and therefore appears bright.

If in dim light, it reflects little and seems indistinct.

It is not so easy to understand why one object appears red and another green until we learn that surfaces exercise a selective power on the light of the sun or other source of illumination.

Every surface decompoeses the particular light with which it is illuminated, absorbing some of the constituent rays while reflecting or scattering others in all directions.

(I'm here refraining from any consideration of the different kinds of reflection and reflective surfaces, and from a discussion of the appearance of objects exposed to colored light.)

A red book, as it decomposes the light which falls upon it, absorbs or annihilates all the rays but the red.

The rays are reflected, some of them reaching the eye, which instantly conveys to the brain, via the optic nerve, the sensation of red.

A green book, on the contrary, has the power of absorbing all the rays but the green; these are the ones reflected.

A white object is merely one which reflects a large percentage of the rays, including all colors so balanced as to give the effect of absence of color white.

A black object is one which absorbs nearly all the rays which reach it.

A gray object absorbs some rays and reflects others, doing so without disturbing the relative proportion of waves as they exist in the light illuminating the object.

Few objects appear as of a single pure color, however, or absolutely white or black hence this description is far from complete.